What Are Electrochemistry and Galvanic Cells?
Electrochemistry studies how chemical reactions produce electrical energy (galvanic cells) or how electricity drives chemical reactions (electrolytic cells). Galvanic cells use redox to generate voltage.
A galvanic (voltaic) cell is a device where a spontaneous redox reaction produces electrical current. Two half-cells with different electrodes, connected by a salt bridge, create a potential difference (voltage).
- 1↓Anode (−)Oxidation: electrons released
- 2↓Salt bridgeIons flow to balance charge
- 3↓Cathode (+)Reduction: electrons accepted
- 4External circuitElectrons flow through wire as current
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Step-by-step worked examples
In a Zn–Cu galvanic cell, Zn is oxidized and Cu²⁺ is reduced. If E°(Zn²⁺|Zn) = −0.76 V and E°(Cu²⁺|Cu) = +0.34 V, find E°cell.
Anode (Zn): E°anode = −0.76 V Cathode (Cu): E°cathode = +0.34 V E°cell = E°cathode − E°anode = 0.34 − (−0.76) = 1.10 V
In a Mg–Ni cell, E°(Mg²⁺|Mg) = −2.37 V, E°(Ni²⁺|Ni) = −0.23 V. Calculate E°cell.
Mg is more easily oxidized (lower E°), so Mg is anode. Anode: E° = −2.37 V; Cathode: E° = −0.23 V E°cell = −0.23 − (−2.37) = 2.14 V
A galvanic cell produces 0.50 V. If the cathode is Cu²⁺|Cu (E° = +0.34 V), what is E°anode?
E°cell = E°cathode − E°anode 0.50 = 0.34 − E°anode E°anode = 0.34 − 0.50 = −0.16 V
Flashcards
Quick quiz
Q1.In a galvanic cell, which half-reaction occurs at the cathode?
Q2.In a Zn–Cu cell, which is the positive terminal?
Q3.If E°cell = 1.5 V and E°cathode = +2.0 V, what is E°anode?
Q4.Why must E°cell be positive for a galvanic cell?
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Common mistakes
Anode is the positive terminal in a galvanic cell. — Correct: Anode is negative (oxidation site); cathode is positive (reduction).
Electrons flow from cathode to anode through the external circuit. — Correct: Electrons flow from anode to cathode; ions flow through salt bridge.
Any redox reaction can be used in a galvanic cell. — Correct: Only spontaneous reactions (E°cell > 0) produce current.
The salt bridge conducts electrons. — Correct: Salt bridge conducts ions only; electrons travel via external wire.
FAQ
How does a galvanic cell produce electricity?
Spontaneous redox reaction transfers electrons from anode to cathode, creating current through external circuit.
What is the difference between anode and cathode?
Anode: oxidation (−), electrons leave. Cathode: reduction (+), electrons arrive.
Can a galvanic cell be reversed?
Yes—if you apply external voltage, it becomes electrolytic (non-spontaneous reaction).
Why is the salt bridge necessary?
It allows ions to move between half-cells, completing the circuit and balancing charge.